Opinion of the Court. 276 U.S. was the first person who observed its efficacy for that purpose." Similarly, the examiner in the Patent Office who allowed the patent said that Weiss' application was "no more than a broad disclosure of the use of [D. P. G.] without disclosing any details other than those usually employed with accelerators of this class." The patent in suit was applied for November 12, 1921, and was granted March 28, 1922. Weiss had referred in the specifications of this patent to another patent of his which was applied for July 2, 1921, and granted July 11, 1922. This latter patent was for a process for making D. P. G. in large or commercial quantities. In the application for that patent, the patentee pointed out that before his process was discovered D. P. G. could not be made except in small quantities for chemical research because the cost was prohibitive. The validity of the Weiss patent for a process in making diphenylguanidine is not attacked. The new patented process by reason of the lessened cost has resulted in the very great use of D. P. G. for commercial purposes and has been very profitable. But the purpose of securing the patent in suit and maintaining its validity is more ambitious. It is not to protect and preserve the new process already being safely enjoyed, but it is to prevent the use of D. P. G. as an accelerator, however made by any process that may be subsequently discovered. It is to enlarge a monopoly of D. P. G. as an accelerator, and is thus in effect to discourage effort to find other and cheaper means of making it. What we have to decide here is not the priority of discovery of the cheap process of making the accelerator D. P. G., which it is conceded Weiss invented, but whether he was the first person to discover the efficacy of D. P. G. as an accelerator, made by any process, cheap or costly. 358 Opinion of the Court. We feel it necessary to call attention to a lack of relevancy of Weiss' successful process patent in the case before us, because the majority opinion in the Circuit Court of Appeals seems to us erroneously to have confused the credit due to Weiss for the process patent, already conceded, with his right to his present claim of entire monopoly of the use of D. P. G. as an accelerator. The issues and the evidence in this case can not be considered and discussed without reference to a paper read by Dr. George Kratz, a rubber chemist, at the Philadelphia meeting of the American Chemical Society, between the 2nd and the 6th of September, 1919. It was entitled "The Action of Certain Organic Accelerators in the Vulcanization of Rubber," and was a review of the comparative excellence of a number of well-known and used accelerators, as well as that of D. P. G. with T. P. G., in which he found D. P. G. to be very much more active than T. P. G. Then under an experimental part he described the kinds of rubber used, the proportions of rubber and sulphur in the mixture, and the manner in which the accelerator was incorporated and the method of vulcanization. He said: "The rubber used was good quality, first latex, pale crepe, and the same lot was employed in all mixtures. All mixtures were made under standard conditions; the average time of each batch on the mill was 17.5 min. The same proportion of rubber and sulphur-92.5 parts rubber, and 7.5 parts sulphur-was employed in each instance, but the amount of accelerator was varied, according to the conditions of the experiment. "All the accelerators soluble in alcohol were dissolved in the smallest quantity of this liquid and introduced into the rubber in solution. Those not soluble-and this applied to the anhydroformaldehyde bodies only-were Opinion of the Court. 276 U.S. ground to 100 mesh and added to the rubber with the sulphur. After mixing, the mixtures were allowed a recovery period of 24 hrs. before they were vulcanized. Vulcanization was carried on in a platen press of the usual type." The activities of the various substances were compared in the mixture previously mentioned-92.5 parts of rubber and 7.5 parts of sulphur-taking as a standard the effect obtained with one part of aniline, vulcanized for 90 min. at 148° C. The amounts of various substances in the urea series required to effect the same degree of vulcanization as obtained with one part of aniline are shown in Table 1. The paper thus shows that the activity and superiority of D. P. G. as an accelerator over T. P. G. is approximately as 7 is to 1. In the answer to the bill in this case, the Kratz paper was set up as a defense, but although read before September 6th, 1919, it was not published until April, 1920. Under 4886, Revised Statutes, a person who claims to have invented any patentable improvement, is not to be denied a patent because of any printed publication subsequent to his discovery, unless there was publication or public use or sale more than two years prior to his application. Kratz's article was not printed until less 358 Opinion of the Court. than two years before Weiss' application for a patent in November, 1921, and therefore the paper could not be used as a basis for defense against his patent, if his discovery was earlier than the publication. It nevertheless plays a very important part in understanding the facts in this ease. The main and only issue here is divided, by reason of the evidence and the lines of argument pursued, into two parts. The first is the effect of that part of it devoted to Weiss' discovery and his reduction to practice. The second is that part devoted to Kratz's discovery and his reduction to practice. First. It is contended by the petitioner that the file wrapper and evidence show, that the patent was secured by false evidence and is not entitled to the presumption. of validity which ordinarly accompanies the grant. The examiner in the Patent Office three times rejected the Weiss application, the third time by a reference to the Kratz paper. The hearing on that reference was exparte. The third rejection was followed by acquiescence by the examiner because of two affidavits, one by Weiss and one by his fellow chemist Daniels, who claimed to have been with him at the time in the laboratory of the Republic Rubber Company of Youngstown. In these final affidavits, Weiss had said that D. P. G. was produced and actually used " in the vulcanization of rubber goods " during the early part of the year 1919, and Daniels said, "These tests were also carried out in the compounding laboratory for the various departments of the Republic Rubber Company at Youngstown, Ohio, and the accelerator proved to be highly efficient in the actual vulcanization of rubber goods, such as hose, tires, belis, valves and other mechanical goods." It now appears, without contradiction, that the only rubber Weiss made during the early part of the year 1919 from D. P. G. was test slabs of rubber in which D. P. G. was the accelerator, and Opinion of the Court. 276 U.S. that in fact neither he nor anybody in the Rubber Company had vulcanized rubber goods, as Daniels described them, before the Kratz publication. But we do not think this would invalidate the patent, for the reason that the actual fact was that these test slabs of rubber with D. P. G. if proven to be properly vulcanized, as the evidence seems to show, were a demonstration of the utility of D. P. G. as an accelerator and were a completed and demonstrated discovery constituting reduction to practice. Production of rubber-goods for use or sale was not indispensable to the granting of the patent. Hence the affi davits, though perhaps reckless, were not the basis for it or essentially material to its issue. The reasonable presumption of validity furnished by the grant of the patent therefore would not seem to be destroyed. Then it is claimed that the reference to the Kratz paper, which was not attacked by the applicant for its insufficiency as a reference under § 4886 of the Revised Statutes, should be treated as equivalent to a prior patent, the priority of which could only be overcome by evidence eliminating all reasonable doubt. The Barbed Wire Patent, 143 U. S. 275; Deering v. Winona Harvester Works, 155 U. S. 286, 300; Clark Thread Company v. Willimantic Linen Company, 140 U. S. 481, 489. But the Kratz paper was not a prior patent, and while it may be that other circumstances such as a reference to a publication made before the application for the patent may have the effect to require the same convincing proof of earlier discovery to avoid its effect (Westinghouse, etc. Co. v. Catskill, etc. Co., 121 Fed. 831, 834; New England Motor Co. v. Sturtevant Co., 150 Fed. 131, 137; Wendell v. American Laundry Machinery Co., 248 Fed. 698, 700), we do not think that the mere failure to invite the attention of the examiner to the defect of the reference under § 4886, Revised Statutes, calls for the strict rule of proof |